As noted in my previous article Diving into JTAG protocol. Part 1 — Overview, JTAG was initially developed for testing integrated circuits and printed circuit boards. However, its potential for debugging was realized over time, and now JTAG has become the standard protocol for microcontroller debugging. Many Firmware and Embedded engineers first encountered it in this particular context.

With the number of wireless SoCs on the market, “Just add connectivity” is finally a reality! “Just” does a lot of lifting in that phrase. Connectivity, whether wired or wireless, adds numerous layers of complexity to your device. Treating your connectivity as a black box early in development is easy, but this strategy will implode when thousands of devices enter the field - trust me, I know. It’s not enough to test from end to end a few times in the office.

Having covered the Devicetree basics in the previous article, we now add semantics to our Devicetree using so-called bindings: For each supported type, we’ll create a corresponding binding and look at the generated output to understand how it can be used with Zephyr’s Devicetree API. Notice that we’ll only look at Zephyr’s basic Devicetree API and won’t analyze specific subsystems such as gpio in detail.

In the previous article, we configured software using the kernel configuration tool Kconfig, and we’ve silently assumed that there’s a UART interface on our board that is configurable and used for logging. In this third article of the “Practical Zephyr” series, we’ll see how we configure and use hardware. For this, Zephyr borrows another tool from the Linux kernel: Devicetree.